Optimum compaction low void composite bicycle wheel rim

ABSTRACT

A fiber reinforced plastic bicycle wheel rim having an aerodynamic section is formed of two mating halves, without additional structural reinforcing members, using laminations of layers of unidirectional fibers crossing one another and having semicircular layers of non-crossing fibers orientated parallel to a point of tangency, the non-crossing layers being proximate tire well apexes and the spoke bed, including, in a preferred embodiment, a lamination of machinable materials at the braking surfaces.

[0001] Priority is claimed based on U.S. Provisional Patent ApplicationSerial No. 60/400,193 filed Jul. 31, 2002 and having the same title andinventor as this application.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention is an improved two-piece bicycle wheel rim havingintegral mating portions and improved composite layup providing lighterweight and increased strength in an economical manner without separatejoining or reinforcing pieces.

[0004] 2. Description of Related Art

[0005] Basic principles of optimum compaction low void composite moldingthe bicycle industry are described in U.S. Pat. Nos. 5,624,519 and6,270,104, sharing a common assignee with this application. Thedisclosures in U.S. Pat. Nos. 5,624,519 and 6,270,104 are incorporatedby reference as if fully set forth herein.

[0006] Metal wheel rims have long been made by bending a straightextrusion, bar or other shape to a circular form and then joining theends to make a closed circle. Typical joining may include inserts suchas U.S. Pat. No. 4,938,540, plugs of metal or even wood, or by weldingas in European Patent Office Publication No. 0579525A1. These patentsare incorporated by reference as fully set forth herein.

[0007] Owing to the different strength properties of composite fibrereinforced plastics, particularly the high tensile strength and highstiffness of materials such as carbon fibre, the base material is formedto shape prior to curing. Three typical methods of forming a wheel orwheel rim from carbon fibre reinforced plastic are know. These include acored composite in which the high strength skin surrounds a core such afoam core, U.S. Pat. No. 5,061,013, a solid composite such as U.S. Pat.6,347,839 B1 in which composite laminations have no designed endopenings or different density materials between interior and exteriorsurfaces and a partially hollow but plugged construction such as U.S.Pat. No. 6,398,313 B1 where two hollow halves have interior inserts andexterior reinforcements at joining ends. The disclosures in these threepatents are incorporated by reference as if fully set forth herein.

[0008] The invention avoids the drawbacks of the prior art using generalprinciples of optimum compaction low void composite constructionspecially adapted to the unique shape and structural requirements ofwheel rims using a combination of laminates incorporating fibers atdifferent angles relative to one another, a curved auto-centering plugin one half at one end mating with a receptacle in an opposite,identical half further using unidirectional layers in key areas of therim edges and spoke bed . A preferred embodiment further combines thepreferred carbon fibre reinforced epoxy laminate structure withmachinable and tough breaking surface portions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a top plan view of one half of the wheel rim.

[0010]FIG. 2 is a sectional view showing the laminate schedulesschematically.

[0011]FIG. 3 is a plan view showing a sidewall lamination.

[0012]FIG. 4 is a plan view showing a wide tire well lamination.

[0013]FIG. 5 shows a narrow tire well lamination.

[0014]FIG. 6 shows the bladder and pressure intensifier arrangement.

[0015]FIG. 7 shows a mold for forming a wheel rim in accordance with theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] A wheel rim 10 is formed of fiber reinforced plastic resin.Preferrably this is formed predominantly of a high modulus fiber, suchas carbon fiber, in an epoxy matrix, with special structural locationscontaining other fibers commensurate with needs in areas having uniqueperformance and/or manufacturing requirements, such as brake surfaces.Thus, strong, but more easily machinable fibers, such as glass can beused in certain areas, and tougher fibers, such as Kevlar, can be usedin high impact areas.

[0017] The fibers are aligned in laminations such as taught in U.S. Pat.Nos. 5,624,519 and 6,270,104 sharing a common assignee with thisapplication. By using a series of 0-45-90 degree alignments, the highstrength and high modulus properties of carbon fiber can be used toadvantage to produce a shape of complex curvature having substantiallyuniform strength in the needed directions in the finished structure,while the optimum compaction and low void methods, as improved for wheelrims as taught herein, produces the finished structure having asubstantially uniform density. Optimum fiber areal weights substantiallyabove the industry standards are also permitted by the product andprocess taught herein.

[0018] Rim 10 as shown as a high performance road racing rim adapted toreceive a conventional glued-on “tubular” or “sew-up” tire in which thetire and tube are formed together as a unit and this unit is adhesivelyaffixed to the tire well 12 and further mechanically held in place byvirtue of the inflation pressure in the tube, compressing the unitaround the rim 10. As shown in FIG. 1, rim 10 is formed in halves aswill be more fully described below.

[0019] Tire well 12 extends between left and right apexes 14, 16. Theseapexes 14, 16 are slightly radiused while the well 12 is smoothly curvedwith a dimension corresponding to that needed to receive a highperformance “sew-up” tire with a diameter of around one inch, typically21 to 28 mm. Sharp changes in curvature in tire well 12 are avoided tomaximize utilization of standard tires and to maximize their adhesionand other performance.

[0020] Extending downwardly from apexes 14, 16 are braking surfaces 18,20 which join left and right walls 22, 24. Walls 22, 24 then join atspoke bed 26. The curvature of spoke bed 26 and walls 22, 24substantially conforms to the trailing two thirds of an aerodynamic foilshape having a thickness of about 20 mm and a chord of about 40 mm,recognizing that the braking surfaces 18, 20 are substantially flat andslightly less than 20 mm across.

[0021] Keeping in mind that specific lamination schedules are generallyin accordance with the teachings of the aforementioned US. Pat. Nos.5,624,519 and 6,270,104, certain wheel rim advantages are shown in theschematic arrangements of laminations. It will be understood that eachindividual lamination described is itself comprised of componentunidirectional fiber layers arranged at 0-45-90 degrees relative to oneanother.

[0022] Tire well 12 is formed of an outer lamination 30 and an innerlamination 32. Laminations 30, 32 overlap apexes 14, 16 and extend underbraking surfaces 18, 20.

[0023] Braking surface laminations 34, 36 can advantageously use fibersof composition different from high strength, high modulus carbon forseveral reasons, both with or without portions of carbon fiber. Brakingsurfaces 18, 20 perform best when used in conjunction with the highlydeveloped bicycle caliper brakes, when surfaces 18, 20 are machined to ahigh level of smoothness and trueness.

[0024] Other fibers, relative to carbon fiber, have improved propertiesin ease of machining and improved wear on the tools used to machinefiber reinforced plastics which use them. Brake surfaces 18, 20 are alsosubject to wear and damage when in use, particularly as a result ofcontamination by foreign objects such as sand, stones, road tar and thelike. Other materials have greater toughness than carbon fiber, thusother materials may be substituted. Finally, the surfaces presented by amachined fiber reinforced plastic using materials other than carbonfiber may have more optimum coefficient of friction with typicalelastomeric caliper brake shoes, thus other materials may besubstituted. Glass reinforced plastic has been used successfully inthese areas. Other reinforcements having improved machinability,toughness and frictional properties may also be used. Typical fiberreinforcement may include Kevlar, glass, ceramic, other plastics such asa nylon, Spectra, Vectran or other high temperature plastic, or metalssuch as aluminum or ferrous metals. Similarly, outer layer 30 is themost vulnerable to road contact damage and might also obtain advantagefrom the use of alternative materials, either as a layer or layers, oras individual fibers combined with carbon fibers in a custom layer.

[0025] Considerations in forming the brake wall areas are to includefiber reinforcement in outer plies of a lamination, including an addedlamination or bonding a separate piece such as a ring made of Aluminumor some other sheet material.

[0026] Spoke bed 26 and walls 22, 24 are formed of overlapped innerlamination 40, outer lamination 38 and middle lamination 42. Laminations38, 40 and 42 effectively form an all carbon fiber reinforced plasticsandwich with voids therebetween eliminated by the compaction process.If each lamination uses, for example, eight unidirectional plies withtheir fibers oriented at 0-45-90 degrees relative to one another, 24 plyquasi-isotropic walls would be formed. Indeed, quasi-isotropicproperties would result from as few as four plies, per lamination, withthe described fiber orientation.

[0027] Outer layer or lamination 38 is actually formed from two mirrorimage semicircular shapes 70, as shown in FIG. 3, butted at the bottomof the rim 10. Bottom inner layer 54 and bottom middle layer 56 bridgethe joint between the two portions of lamination 38. Braking surfacelaminations 34, 36 are laid outward of laminations 38.

[0028] Three “0 degree” bundles of fibers are included in the preferredembodiment. Between layers 54 and 56 spoke bed is captured “0 bundle”58. Left apex “0 bundle” 60 and right apex “0 bundle” 62 are capturedbetween layers 30, 32 at each tire well apex. These bundles, 58, 60, 62perform important structural functions. As described above, apexes, 14,16 and spoke bed 26 are highly loaded. The term “0 bundle” is used todescribe, in these three locations, straight fiber bundles with nocrossing orientation. These bundles are formed in respective circles atapexes 12, 14 and spoke bed 26 such that the individual fibers presentthemselves parallel to the direction of travel of the bicycle at thepoint of tangency, or contact of the tire with the road surface, andperpendicular to the spokes. No substantial side component is present inthe orientation of these layers, as compared to the 0-45-90 orientationof the laminations 30, 32, 34, 36, 38, 40, 42, 54 and 56 which form thebalance of the structure. Thus, strength and stiffness is specificallyapplied in desired directions relative to the road surface and thespokes.

[0029] Further, these bundles, 58, 60, 62 are readily compressed in thecomplex shape of a hollow wheel rim 10 which will enable substantialelimination of voids between laminations 30, 32, 34, 36, 38, 40, 42 54and 56 and bundles 58, 60, 62 by application of pressure to a bladder64. For ease of manufacture, the geometry described herein permits theuse of a bladder 64 formed of a simple tube, with the auxiliary use ofpressure intensifiers 66 proximate apexes 14, 16 and spoke bed 26.Pressure intensifiers 66 are preferably formed of simple arc sectionedribbons of silicone, or some other suitable elastomer that conforms toshape, tends to expand when heated and does not permit epoxy adhesion.

[0030] As bladder 64 and pressure intensifiers 66 are used at hightemperatures and pressures in close contact with epoxy impregnatedlaminations, the use of economical and easily replaceable bladders 64,and intensifiers 66 yields a functionally superior, yet economicallyfeasible molding method.

[0031] Rim half 160 is formed with a male plug 162 and a femalereceptacle 164 so that two identical halves can be matinglyinterconnected and glued to form a single rim 10. It will be noted thatplug 162 has a projecting arc portion 166 and a tapered neck portion168. These fit corresponding machined shapes in receptacle 164. Neck 168provides a centering effect to insure precise alignment of the twohalves and maintains an adequate glue thickness. Epoxy can preferably beused as an adhesive, and performs best when a uniform thickness coatsthe mating portions 162, 164. Further, uniform thickness, especiallygiven the arc shape of portions 162, 164 is particularly important in awheel rim to avoid any slight imbalance that would be caused byinconsistent quantities of epoxy used as adhesive. Forming the complexarced, mating portions 162, 164 is a particular advantage in the optimumcompaction, low void molding process used herein.

[0032] Semicircular lamination 70 and layups 72, 74 are shown forillustration of the formation of rim 10. In fact, depending on thespecific schedule of laminations, a variety of different combinationsand configurations can be used consistent with the teachings herein.Additionally reinforcing ribbons and doublers can also be used, added tospecific locations in the rim, such as where spoke holes are to bemachined. The overlapable layups shown have darts 76, 78 staggered suchthat they permit curvature of layups 72, 74 to the three dimensionalshape of laminations during the molding process. The spacing of darts76, 78 is such that dart 76 will not be located immediately adjacentdart 78, and vice versa, thereby having a length of continuous fibers inat least one of the laminations. Further, because the laminations 72, 74will be curved, the opposed edges of darts 76, 78 will overlap oneanother, providing further fiber strengthening when compacted and curedin an epoxy matrix.

[0033] Laminations 30, for example can be formed of a somewhat widerlayup 72 when compared to lamination 54 because of they width of tirewell 26. The specific layup width will also depend on the size of therim, such as a 21 mm rim v. a 25 mm wide rim, and the configuration,such as an aerodynamic section shown, or a minimum weight section whichmight have a shorter chord. Rim diameter will also be a factor.Typically, lamination 38 will be the semicircular form 70, whilelaminations 30, 32, 54, 56 will be one of the flat layups 72, 74, withdimensions adjusted based on rim configuration.

[0034] Braking surfaces 18, 20 may have their own individualsemicircular layups. As described above, these may advantageously use avariety of fiber or cloth laminations. Alternatively, a single circularbonded ring, such as formed of metal could also be used. Further,separate braking surfaces may be dispensed with in rims for certainconditions Thus, for certain competitive conditions, such as a cleanflat race course in good weather, special braking surfaces may bedispensed with, while for difficult conditions, such as poor weather ormountainous courses requiring aggressive and frequent braking, rimshaving special braking surfaces may be more advantageous.

[0035] Mold 90 is formed of two halves 92, 94 defining a chamber 96. Inthe preferred rim—for tubular tires—a solid mandrel 98 is placed inchamber 96 to define the shape for tire well 12. In alternativeembodiments a different mandrel configuration could be used, such assolid, partially solid or inflatable, to define flanges to receive aclincher type tire. A conduit 100 enables communication between bladder52 and an outside pressure source, preferably compressed air.

[0036] While the present invention has been disclosed and described withreference to a single embodiment thereof, it will be apparent, as notedabove that variations and modifications may be made therein. It is,thus, intended in the following claims to cover each variation andmodification that falls within the true spirit and scope of the presentinvention.

In accordance with my invention, I claim:
 1. A wheel rim formed of fiberreinforced plastic comprising. the wheel has a structural portion andleft and right braking surfaces; said structural portion is formedpredominantly of a high modulus fiber in a plastic matrix; said brakingsurfaces are formed of strong, but more easily machinable fibers in aplastic matrix; said high modulus fibers are aligned in laminationsformed of a series of 0-45-90 degree alignments; the wheel is formed ina shape of complex curvature having substantially uniform strengthhaving a substantially uniform density. the ratio of said fiber to saidplastic in said wheel is substantially above 60%; said wheel is formedof first and second substantially identical semicircular halves; saidfirst half has a first male plug at one end and a first femalereceptacle at the opposite end separated by an arc portion; said firstmale plug has a first tapered neck portion; said second half has asecond male plug at one end and a second female receptacle at theopposite end separated by an arc portion; said second male plug has asecond tapered neck portion; the wheel is assembled by matinglyinterconnecting and adhesively bonding said first male plug with saidsecond female receptcle, and said second male plug with said firstfemale receptacle such that said first tapered neck portion tends tocenter said first male plug and preserve adequate adhesive coating, andsaid second tapered neck portion tends to center said second male plugand preserve adequate adhesive coating.
 2. The wheel of claim 1, furthercomprising: the wheel is formed with a tire well that extends betweenleft and right apexes; said apexes are slightly radiused; said well issmoothly curved to receive a tire with a diameter of around one inch;extending downwardly from said apexes are left and right brakingsurfaces; said braking surfaces join left and right walls; said left andright walls join at a spoke bed; the curvature of said spoke bed andleft and right walls substantially conforms to the trailing two thirdsof an aerodynamic foil shape having a thickness of about 20 mm and achord of about 40 mm; said braking surfaces are substantially flat andslightly less than 20 mm across.
 3. The wheel of claim 2, furthercomprising: said tire well is formed of a first outer lamination and afirst inner lamination, which first laminations overlap said apexes andextend under said braking surfaces.
 4. The wheel of claim 3, furthercomprising: said spoke bed and walls are formed of overlapped secondinner lamination, second outer lamination and a first middle lamination;said second laminations and said first middle lamination effectivelyform an all carbon fiber reinforced plastic sandwich with voidstherebetween eliminated by the compaction process; said secondlaminations and said first middle laminations form quasi-isotropic wallsbecause of the directions of fiber orienation.
 5. The wheel of claim 4,further comprising: three 0 degree bundles of fibers are arrangedaligned with the arc of the wheel at said spoke bed said left apex andsaid right apex.
 6. The wheel of claim 3, further comprising: saidbraking surfaces are machined to a high level of smoothness andtrueness; said braking surfaces are formed of a plastic matrix withfibers formed of materials that have greater toughness than carbonfiber; said machined braking surfaces have a greater coefficient offriction with elastomeric caliper brake shoes than carbon fiberreinforced plastic surfaces.
 7. The wheel of claim 3, furthercomprising: said wheel rim is formed to have flanges to receive aclincher type tire.
 8. A method of forming a bicycle wheel rim fromlaminations of fiber reinforced plastic resin comprising: forming anuncured rim component layup with an outer layer from two mirror imagesemicircular shapes, said shapes are butted at the bottom of the rimcomponent; arranging a bottom inner layer and bottom middle layer tobridge the joint between the two layers; laying up braking surfacelaminations outward of said two layers; positioning three “0 degree”bundles of fibers located, respectively, between the layers that formthe spoke bed, between the layers that form the left apex and andbetween the layers that form the right apex of the rim section; placingsaid layup in a mold; applying pressure compressing said layersoutwardly against said mold so that voids between said laminations aresubstantially eliminated; curing said resin to result in a rimcomponent.
 9. The wheel forming method of claim 8, further comprising:using a bladder to apply said pressure; using pressure intensifiers toapply pressure from said bladder against said apexes.
 10. The wheelforming method of claim 8, further comprising: said rim component beinga first rim component; a second rim component being formed using thesame method as sad first rim component; forming said first rim componentwith a first integral projecting portion and a first receivingreceptacle; forming said second rim component with a second integralplug and a second receiving receptacle; joining said first plug to saidsecond receptacle and joining said second plug to said first receptacleto form a complete wheel rim.
 11. The wheel forming method of claim 8,further comprising: said resin is an epoxy resin; substantially all ofsaid fibers are carbon fiber.
 12. The wheel forming method of claim 8,further comprising: said resin is an epoxy resin; said brake surfacesare formed from an epoxy resin with a substantial portions of saidfibers being glass fibers; substantially all of said fibers in all thelayers except the layers forming said brake are carbon fiber.
 13. Thewheel forming method of claim 8, further comprising: said first andsecond plugs each have a projecting arc portion and a tapered neckportion; said projecting arc portion and a tapered neck portions fitcorresponding machined shapes in said first and second receptacles saidnecks providing a centering effect to insure precise alignment of thefirst and second rim components and maintain an adequate glue thickness.14. The wheel forming method of claim 8, further comprising: theoverlapable layers have darts staggered such that they permit curvatureto the three dimensional shape of laminations during the moldingprocess; said darts are spaced such that opposed darts will not belocated immediately adjacent one another, thereby having a length ofcontinuous fibers in at least one of the laminations; and saidlaminations are formed so that as they are curved, the opposed edges ofsaid darts will overlap one another, providing further fiberstrengthening when compacted and cured in an epoxy matrix.
 15. The wheelforming method of claim 8, further comprising: said mold is formed oftwo halves defining a chamber; a solid mandrel is placed in chamber todefine the shape for tire well.
 16. The wheel forming method of claim 8,further comprising: said mold is formed of two halves defining achamber; a mandrel is placed in chamber to define flanges to receive aclincher type tire.